Abstract:
Herbal lemongrass is widely used in Thai cooking and is important ingredient in Thai traditional sour soup, Tom Yum. At present, some commercial instant sour soup pastes exhibit flavor loss during their processing. In this study, lemongrass oil was of interest for finding a suitable way to keep the flavor as fresh products by encapsulation technique. The encapsulation of lemongrass oil by spray drying was investigated with respect to effects of oil loading, emulsion size and inlet air temperature. The effects of various process parameters on the emulsion size and encapsulation efficiency during spray drying with an aim to obtain the high retention of flavor after drying. Because citral is recognized as the major chemical compound in the extracted lemongrass oil it was used as the indicator compounds to evaluate the encapsulation efficiency. The results showed that lemongrass oil microcapsules were successfully produced by spray drying, using modified starch and gum arabic with maltodextrin (1: 3). The encapsulated lemongrass oil presented spherical shape with smooth and extensive dented surface. The mean particles size was 10-40 m. Spray drying at below 40 wt% oil loading with the modified starch could provide higher retention of citral about 100%. However, gum arabic with maltodextrin (1: 3) showed higher stability of encapsulated lemongrass oil than modified starch. The effect of inlet air temperature on the citral retention after spray drying was insignificant. However, the emulsion size could affect a significant on the citral retention. The smaller emulsion size could also provide the higher retention of citral.